GL_EXT_texture_sRGB
http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_sRGB.txt
	GL_SRGB_EXT 0x8C40
	GL_SRGB8_EXT 0x8C41
	GL_SRGB_ALPHA_EXT 0x8C42
	GL_SRGB8_ALPHA8_EXT 0x8C43
	GL_SLUMINANCE_ALPHA_EXT 0x8C44
	GL_SLUMINANCE8_ALPHA8_EXT 0x8C45
	GL_SLUMINANCE_EXT 0x8C46
	GL_SLUMINANCE8_EXT 0x8C47
	GL_COMPRESSED_SRGB_EXT 0x8C48
	GL_COMPRESSED_SRGB_ALPHA_EXT 0x8C49
	GL_COMPRESSED_SLUMINANCE_EXT 0x8C4A
	GL_COMPRESSED_SLUMINANCE_ALPHA_EXT 0x8C4B
	GL_COMPRESSED_SRGB_S3TC_DXT1_EXT 0x8C4C
	GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
	GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
	GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F